Damper

ABSTRACT

The present disclosure relates to a frequency tuned damper having a vibration body ( 19 ) and at least one elastic element ( 11, 13, 15, 17 ) which connects the vibration body to a surface ( 21 ), the vibrations of which is to be dampened. The elastic element has a wide portion ( 29 ) and a narrow portion ( 31 ) disposed at different locations on an axis ( 39 ) which is substantially parallel with the normal of the surface. The wider portion has a cavity ( 41 ), and the wide and narrow portions are inter-connected by a transition portion ( 43 ). The part of the narrow portion that is closest to the transition portion fits inside the cavity, as seen in the direction of the axis, such that the narrow portion can be pushed at least partly into the cavity, thereby flexing the transition portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of copending U.S. application Ser.No. 12/594,514, filed on Oct. 2, 2009, which is the National Phase ofPCT International Application PCT/SE2007/000357, filed on Apr. 16, 2007,all of which are hereby expressly incorporated by reference into thepresent application.

TECHNICAL FIELD

The present disclosure relates to a frequency tuned damper having avibration body and at least one elastic element which is adapted toconnect the vibration body to a surface, the vibrations of which is tobe dampened, the elastic element having a wide portion and a narrowportion disposed at different locations along a longitudinal axis whichis substantially parallel with the normal of the surface when the damperis mounted, one of said portions being adapted to attach the elasticelement to the vibration body and the other to attach the elasticelement to the surface, the wider portion having a cavity.

BACKGROUND

Such a damper is disclosed e.g. in EP 1303710. Dampers of this kind maybe used to dampen vibrations with one or more target frequencies. Forinstance, the damper may be installed in the steering wheel of avehicle, and may be used to dampen vibrations in the steering wheelcorresponding to the idling rpm of the vehicle. One technical issueassociated with such dampers is how to make them useful for combatingvibrations of various kinds.

SUMMARY

An object of the present disclosure is to provide a frequency tuneddamper that is capable of dealing with vibrations that are not addressedby the known device.

This object is achieved by the frequency tuned damper defined in claim1.

More specifically, in a frequency tuned damper of the initiallymentioned kind, the wide and narrow portions are then inter-connected bya transition portion, and the part of the narrow portion that is closestto the transition portion fits inside the cavity, at the portion thereofthat is in the wide portion and closest to the transition portion, asseen in the direction of the axis, such that the narrow portion can bepushed at least partly into the cavity, thereby flexing the transitionportion.

This gives the elastic element a comparatively low stiffness in thedirection of the longitudinal axis, and allows the damper to dampenvibrations with relatively low frequencies in that direction.

The elastic element may be circular symmetric about the longitudinalaxis. This gives the elastic element similar properties in forvibrations having their amplitude in the plane of the surface, such thatthe orientation of the elastic element around the element is notcritical.

The transition portion may have the shape of an annular disc, centeredwith respect to the longitudinal axis. This is particularly useful forlow frequency vibrations. Alternatively, the transition portion may havethe shape of an envelope surface of the frustum of a cone, centered withrespect to the longitudinal axis. This makes the elastic elementsuitable for dealing also with somewhat higher frequencies.

The cavity may be open in the direction of the longitudinal axis at thewide portion. This makes is possible to insert a tool in the cavity thatfacilitates the mounting of the frequency tuned damper. The cavity mayfor this purpose also extend into the narrow portion of the elasticelement.

The elastic element may be made of silicone rubber, although many otherelastic materials are conceivable.

The damper may comprise an intermediate member, which is adapted toconnect the elastic element/elements to the vibration surface.

The elastic element may be attached to the vibration body by means of afirst circumferential groove in the elastic element engaging with acircumferential projection inside a cavity of the vibration body. Theelastic element may further comprise a second circumferential groove forattaching the elastic element to the vibration surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically a frequency tuned damper.

FIG. 2 shows an exploded view of a damper having four elastic elementsand being attached to a vibration surface.

FIG. 3 shows a front view of the damper in FIG. 2.

FIGS. 4a and 4b illustrate a cross-section through the damper of FIG. 3.

FIG. 5 illustrates an alternative embodiment of a damper.

FIG. 6 illustrates an elastic element of a first type.

FIGS. 7a and 7b illustrate an elastic element of a second type.

DETAILED DESCRIPTION

The present invention relates in general to frequency tuned dampers. Anexample of such a damper 1 is schematically illustrated in FIG. 1. Thedamper 1 is used to dampen vibrations in a surface 3, and comprises avibration body 5 and at least one elastic element 7, which are attachedto the surface 3 and together provide a spring-mass system.

The mass m of the vibration body 5, and the stiffness k and damping c ofthe elastic element 7 are selected to provide a damping effect on thesurface 3, which can be expected to vibrate at a predetermined targetfrequency. When the surface vibrates at this frequency, the vibrationbody is caused to oscillate at the same frequency as the surface but outof phase with the latter, such that the vibration of the surface issubstantially dampened. The vibration body may vibrate with an amplitudesubstantially greater than the vibration amplitude of the surface. Thegeneral concept of a frequency tuned damper as illustrated in FIG. 1 iswell known per se.

The following disclosure presents an elastic element for use in afrequency tuned damper, which is suitable for dealing with vibrations inup to three dimensions in a vibrating surface. As illustrated in FIG. 1the damper may thus dampen vibrations in the x- and y dimensions(parallel with the surface 3) as well as in the z dimension (parallelwith the normal of the surface 3). It should be noted that the elasticelement may provide different spring characteristics (stiffness,damping) in different dimensions. Thus, the damper may be used to dampenvibrations in the surface 3 having different frequencies in differentdimensions.

FIG. 2 shows an exploded view of a damper having a vibration body 19 andfour elastic elements 11, 13, 15, 17, and being attached to a vibrationsurface 21. The vibration body may be made of a material with relativelyhigh density, such as cast iron or the like. The elastic elements may bemade of different elastic materials. Silicone rubber is one suitableexample as a silicone rubber elastic element retains its stiffness anddamping to a great extent even if the temperature varies.

The vibration surface 21 is not to be regarded as a part of the damper,as the purpose of the damper is to reduce vibrations in a surfacealready existing in a structure. However, the elastic elements may alsobe connected to the vibration surface via an intermediate member, whichmay then be regarded as a part of the damper.

In the illustrated example, the damper may be attached to the vibrationsurface 21 by pushing each elastic element, e.g. 13, through acorresponding opening 23 in the vibration surface until a first groove25 in the elastic element 13 forms a grip on the rim of the opening 23.A part of the elastic element is further pushed through a correspondingopening 26 into the interior of the vibration body 19 until a secondgroove 27 on the elastic element 13 forms a similar grip on thevibration body 19. The elastic element will be described in greaterdetail below. A number of alternative ways of mounting the elasticelement exists as the skilled person realizes.

FIG. 3 illustrates a front view of the damper in FIG. 2. As illustrated,the vibration body 19 is attached to the vibration surface 21 by meansof four elastic elements 11, 13, 15, and 17, which are arranged in thecorners of a rectangular formation. Needless to say, other layouts areof course conceivable as well as other numbers of elastic elements.

FIGS. 4a and 4b illustrate a cross-section through the damper of FIG. 3,where FIG. 4b shows an enlarged part of FIG. 4a , and FIG. 4a shows thefull cross-section along the line A-A in FIG. 3. Generally, asillustrated in FIG. 4b , the elastic element 13 has a wide portion 29and a narrow portion 31 (the wide portion being wide as compared to thenarrow portion and vice-versa). The wide portion 29 is attached to thevibration surface 21 by means of the circumferential groove 25 in thewide portion engaging the rim 33 of the opening (23, see FIG. 2) in thevibration surface 21. In a corresponding manner, the narrow portion 31is attached to the vibration body 19 by means of the circumferentialgroove 27 in the narrow portion engaging with a circumferentialprojection 35, which projects from the wall of a cavity 37 in thevibration body 19. By means of this arrangement, the vibration body 19is resiliently suspended in relation to the vibration surface 21. Thewide and narrow portions 29, 31 are disposed at different locationsalong a longitudinal axis 39 which is substantially parallel with thenormal of the surface 21.

The cavity 37 in the vibration body 19 may be sufficiently large toallow a reasonably great vibration amplitude without coming in directcontact with the wide portion 29 of the elastic element (therebyradically increasing the stiffness). However, it may be useful to letthe wide portion come in contact with, and stop the movement of, thevibration body before the vibration body comes into contact with thevibration surface, as strong noise would otherwise be generated. In theillustrated damper the region close to reference sign 37 provides thisstopping feature which stops the vibration body from touching thevibration surface.

FIG. 5 illustrates an alternative damper arrangement. In thisarrangement, the vibration body 19′ is instead attached to the wideportion 29 of the elastic element, and the vibration surface 21′ isattached to the narrow portion 31 of the elastic element.

FIG. 6 shows the elastic element of FIG. 4b . As illustrated, the wideportion 29 has a cavity 41. In the illustrated elastic element, thecavity 41 is open towards the wider end, and may thus be used, in themounting procedure, to receive a tool (not shown) that is used to insertthe elastic element into the opening of the vibration surface and intothe cavity of the vibration body. The cavity 41 may, but need not,extend into the narrow portion of the elastic element.

The wide 29 and narrow 31 portions are inter-connected by a transitionportion 43, which extends circumferentially from the narrow portion andto a great extent radially with respect to the longitudinal axis 39 ofthe elastic element. In this elastic element, the transition portion hasto a great extent the shape of a flat annular disc or ring, centeredwith the longitudinal axis 39.

The part 45 of the narrow portion that is closest to the transitionportion 43 has a smaller radial extension than the portion 47 of thecavity 41 that is closest to the transition portion 43, and thereforefits inside this part of the cavity as seen in the direction of the.axis 39. This allows, as compared to the known device, a relatively lowstiffness in the z-dimension, i.e. in the direction parallel to thenormal of the vibration surface (cf. FIG. 1). Therefore, the damper canbe used to reduce vibrations with comparatively low frequencies in thez-direction. As the dimensions of the relevant part of the narrowportion are smaller than the relevant part of the cavity, the narrowportion can be pushed, at least to some extent, into the cavity, therebyflexing the transition portion 43. It should be noted though, that thenarrow portion need not actually enter the cavity during operation ofthe damper. However, the fact that the narrow portion may be pushed intothe cavity provides for a relatively low stiffness in the z-direction.

The elastic element in FIG. 6 is circular symmetric about thelongitudinal axis, which implies that the damper will have the sameproperties in the x-and y-dimensions as illustrated in FIG. 1. In thiselement, the outer diameter D of the narrow portion 31 close to thetransition portion 43 is smaller than the diameter L of the cavity 41 inthe wide portion 29, at the portion 47 closest to the transitionportion. More particularly, the diameter of the cavity L is about 1.43times the diameter D of the narrow portion in the illustrated example.

The circular symmetry is advantageous, as the elastic element need notbe fixed in any particular orientation around the axis 39 when mounted.However, if different properties in x- and y-dimensions are desired, itis possible e.g. to provide an elastic element which has an ellipticcross-section at some locations along the axis 39. Other shapes are ofcourse also possible.

FIGS. 7a and 7b illustrate an elastic element of a second type, whereFIG. 7b illustrates a cross-section along the line A-A in FIG. 7a . Inthis embodiment, the transition portion 43′ has the shape of an envelopesurface of a frustum of a cone. This gives a somewhat higher stiffnessin the z-dimension and thus makes the damper useful for dampeningsomewhat higher frequencies than the version of FIG. 6.

The invention is not restricted to the described embodiments and may bealtered in different ways within the scope of the appended claims.

The invention claimed is:
 1. A dampening system comprising: a vibrationsurface, wherein the vibration surface experiences vibrations normal tothe vibration surface; a vibration body; and at least one elasticelement which connects the vibration body to the vibration surface suchthat the vibration body forms an elastically suspended mass, the elasticelement having a wide portion and a narrow portion disposed at differentlocations along a longitudinal axis which is substantially parallel witha normal of the vibration surface, one of said portions being adapted toattach the elastic element to the vibration body and the other to attachthe elastic element to the vibration surface, the wide portion having acavity, wherein: the wide and narrow portions are inter-connected by atransition portion, the elastic element and the vibration body are tunedto said vibrations of the vibration surface such that the vibrationsnormal to the vibration surface are counteracted through phase-shiftedmovement of the vibration body, and a maximum radial extension of thenarrow portion is smaller than a minimum radial extension of the cavity,such that the narrow portion can be pushed at least partly into thecavity of the wide portion, thereby flexing the transition portion. 2.The system according to claim 1, wherein said at least one elasticelement is circular symmetric about the longitudinal axis.
 3. The systemaccording to claim 1, wherein the transition portion has the shape of anannular disc, centered with respect to the longitudinal axis.
 4. Thesystem according to claim 1, wherein the transition portion has theshape of an envelope surface of the frustum of a cone, centered withrespect to the longitudinal axis.
 5. The system according to claim 1,wherein the cavity is open in the direction of the longitudinal axis atthe wide portion.
 6. The system according to claim 1, wherein the cavityextends into the narrow portion of the elastic element.
 7. The systemaccording to claim 1, wherein the elastic element is made of siliconerubber.
 8. The system according to claim 1, wherein the elastic elementis attached to the vibration body by means of a first circumferentialgroove in the elastic element engaging with a circumferential projectioninside a cavity of the vibration body.
 9. The system according to claim8, wherein the elastic element comprises a second circumferential groovefor attaching the elastic element to the vibration surface.
 10. Thesystem according to claim 1, wherein a mass of the vibration body, astiffness of the elastic element, and a damping of the elastic elementare selected to cause the vibration body to be tuned to oscillate at apredetermined target frequency normal to the vibration surface.
 11. Thesystem according to claim 1, wherein the vibration surface additionallyexperiences vibrations parallel to the vibration surface, and whereinthe elastic element and the vibration body are tuned to said vibrationsof the vibration surface such that the vibrations normal to thevibration surface as well as the vibrations parallel to the vibrationsurface are counteracted through phase-shifted movement of the vibrationbody.
 12. A method of providing a frequency tuned damper attachable to avibration surface for damping vibrations normal to the vibrationsurface, said method comprising: providing a vibration body; andproviding at least one elastic element which is adapted to connect thevibration body to the vibration surface such that the vibration bodyforms an elastically suspended mass, the elastic element having a wideportion and a narrow portion disposed at different locations along alongitudinal axis which is substantially parallel with the normal of thevibration surface when the damper is mounted, one of said portions beingadapted to attach the elastic element to the vibration body and theother to attach the elastic element to the vibration surface, the wideportion having a cavity, wherein: the wide and narrow portions areinter-connected by a flexible transition portion, the elastic elementand the vibration body are tuned to said vibrations such that vibrationsnormal to the vibration surface are counteracted through phase-shiftedmovement of the vibration body, and a maximum radial extension of thenarrow portion is smaller than a minimum radial extension of the cavity,such that the narrow portion can be pushed at least partly into thecavity of the wide portion, thereby flexing the transition portion. 13.The method according to claim 12, wherein said at least one elasticelement is circular symmetric about the longitudinal axis.
 14. Themethod according to claim 12, wherein the transition portion has theshape of an annular disc, centered with respect to the longitudinalaxis.
 15. The method according to claim 12, wherein the transitionportion has the shape of an envelope surface of the frustum of a cone,centered with respect to the longitudinal axis.
 16. The method accordingto claim 12, wherein the cavity is open in the direction of thelongitudinal axis at the wide portion.
 17. The method according to claim12, wherein the cavity extends into the narrow portion of the elasticelement.
 18. The method according to claim 12, wherein the elasticelement is made of silicone rubber.
 19. The method according to claim12, wherein the elastic element is attached to the vibration body bymeans of a first circumferential groove in the elastic element engagingwith a circumferential projection inside a cavity of the vibration body.20. The method according to claim 19, wherein the elastic elementcomprises a second circumferential groove for attaching the elasticelement to the vibration surface.
 21. The method according to claim 12,wherein the vibration surface additionally experiences vibrationsparallel to the vibration surface, and wherein the elastic element andthe vibration body are tuned to said vibrations of the vibration surfacesuch that the vibrations normal to the vibration surface as well as thevibrations parallel to the vibration surface are counteracted throughphase-shifted movement of the vibration body.